diff --git a/.changeset/bright-suits-reflect.md b/.changeset/bright-suits-reflect.md
new file mode 100644
index 0000000000..4dac0b16e0
--- /dev/null
+++ b/.changeset/bright-suits-reflect.md
@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: `function-name-case` performance
diff --git a/lib/rules/function-name-case/index.js b/lib/rules/function-name-case/index.js
index 40a8db5cc0..45c9ceccf2 100644
--- a/lib/rules/function-name-case/index.js
+++ b/lib/rules/function-name-case/index.js
@@ -54,6 +54,8 @@ const rule = (primary, secondaryOptions, context) => {
 		}
 
 		root.walkDecls((decl) => {
+			if (!decl.value.includes('(')) return;
+
 			if (!isStandardSyntaxValue(decl.value)) return;
 
 			let needFix = false;